Method and system of determining characteristics of a formation

Abstract

Determining characteristics of a formation. At least some of the illustrative embodiments are methods including determining at least one characteristics of a shale formation. The determining may include: collecting optically interacted electromagnetic radiation from a portion of the shale formation; directing a first portion of the optically interacted electromagnetic radiation from the formation to a first multivariate optical element (MOE), the first MOE creates first modified electromagnetic radiation; applying the first modified electromagnetic radiation to a first detector, the first detector creates a first signal; and determining a first characteristic of the shale formation from the first signal.

What is claimed is: 
     
       1. A method of determining characteristics of a formation, the method comprising:
 collecting optically interacted electromagnetic radiation from a portion of a shale formation; 
 directing a first portion of the optically interacted electromagnetic radiation from the shale formation to a first multivariate optical element (MOE), the first MOE creating a first modified electromagnetic radiation; 
 applying the first modified electromagnetic radiation to a first detector, the first detector creating a first signal based on the first modified electromagnetic radiation; 
 determining a first characteristic of the shale formation from the first signal; 
 directing a second portion of the optically interacted electromagnetic radiation to a second MOE distinct from the first MOE, the second MOE creating a second modified electromagnetic radiation; 
 applying the second modified electromagnetic radiation to a second detector distinct from the first detector, the second detector creating a second signal based on the second modified electromagnetic radiation; and 
 determining a second characteristic of the shale formation from the second signal. 
 
     
     
       2. The method of  claim 1  further comprising shining electromagnetic radiation from a light source onto the portion of the shale formation, the shining creates the optically interacted electromagnetic radiation. 
     
     
       3. The method of  claim 2  wherein shining the electromagnetic radiation from the light source further comprises shining the electromagnetic radiation on a portion of a borehole wall on which the shale formation is exposed. 
     
     
       4. The method of  claim 3  wherein the first and second characteristics of the shale formation are determined as the light source, the first MOE, the first detector, the second MOE, and the second detector are disposed within a logging tool moving within the borehole. 
     
     
       5. The method of  claim 4  wherein the first and second characteristics of the shale formation are determined in real-time with the shining and the applying. 
     
     
       6. The method of  claim 2  wherein shining the electromagnetic radiation from the light source further comprises shining the electromagnetic radiation on a core sample removed from the shale formation. 
     
     
       7. The method of  claim 1  wherein the optically interacted electromagnetic radiation emanates from a portion of a borehole wall on which the shale formation is exposed. 
     
     
       8. The method of  claim 1  wherein each of the first and second characteristics is at least one selected from the group consisting of: an indication of total organic content (TOC); an indication of maturation of the shale; an indication of vitrinite reflectivity; an indication of kerogen type; an indication of an amount of a particular kerogen type; an indication of sulfur content; and an indication of the presence heavy metals. 
     
     
       9. The method of  claim 1  wherein the optically interacted electromagnetic radiation emanates from a core sample removed from the shale formation. 
     
     
       10. The method of  claim 1  wherein the first signal created by the first detector is proportional to the first characteristic of the shale formation, and the second signal created by the second detector is proportional to the second characteristic of the shale formation. 
     
     
       11. The method of  claim 1  further comprising:
 applying the second modified electromagnetic radiation to the first detector at designated periods of time, the first detector creating the second signal during the designated periods of time when the second modified electromagnetic radiation is applied the first detector; and 
 determining the second characteristic of the shale formation from the second signal created by the first detector. 
 
     
     
       12. The method of  claim 11  wherein directing the second portion of the optically interacted electromagnetic radiation further comprises:
 moving the first MOE out of an optical path of the optically interacted electromagnetic radiation; and 
 moving the second MOE into the optical path of the optically interacted electromagnetic radiation. 
 
     
     
       13. The method of  claim 11  further comprising:
 directing a third portion of the optically interacted electromagnetic radiation to the first detector to create a third signal, the third portion of the optically interacted electromagnetic radiation incident upon the first detector without encountering a multivariate optical element; and 
 determining an indication of porosity of the shale formation from the third signal. 
 
     
     
       14. The method of  claim 1  further comprising creating the first modified electromagnetic radiation by transmission of the first portion of the optically interacted electromagnetic radiation through the first MOE. 
     
     
       15. The method of  claim 1  further comprising creating the first modified electromagnetic radiation by reflection of the first portion of the optically interacted electromagnetic radiation by the first MOE. 
     
     
       16. A system comprising:
 a tool body for placement into a borehole defining a borehole wall; 
 a light source coupled to the tool body, the light source directing electromagnetic radiation onto a portion of the borehole wall; 
 a first multivariate optical element (MOE) coupled to the tool body and optically coupled to the light source, the first MOE having an optical characteristic responsive to a first characteristic of a shale formation; 
 a first detector coupled to the tool body and optically coupled to the first MOE, the first detector producing a first signal related to the first characteristic of the shale formation; 
 a second MOE coupled to the tool body and optically coupled to the light source, the second MOE having an optical characteristic responsive to a second characteristic of the rock formation; 
 a second detector coupled to the tool body and optically coupled to the second MOE, the second detector producing a second signal related to the second characteristic of the shale formation; and 
 a recording system electrically coupled to the first and second detectors, the recording system recording the first and second signals related to the respective first and second characteristics of the shale formation. 
 
     
     
       17. The system of  claim 16  wherein the first detector produces the first signal in real-time based on optically interacted electromagnetic radiation reflected from a corresponding portion of the shale formation exposed to the electromagnetic radiation directed from the light source onto the portion of the borehole wall. 
     
     
       18. The system of  claim 16  further comprising:
 a pad system coupled to the tool body, the pad system having a first orientation where the pad system is retracted toward the tool body, and the pad system having a second orientation where the pad system is extended to abut the borehole wall, 
 wherein:
 the light source is associated with the pad system; 
 at least one of the first MOE or the second MOE is associated with the pad system; and 
 at least one of the first detector or the second detector is associated with the pad system. 
 
 
     
     
       19. The system of  claim 18  wherein the pad system further comprises a wiper assembly to expose a portion of the shale formation corresponding to the portion of the borehole wall by removal of mud cake from the borehole wall. 
     
     
       20. The system of  claim 19  wherein the wiper assembly removes mud cake based on movement of the tool body within the borehole. 
     
     
       21. The system of  claim 19  wherein the wiper assembly removes mud cake based on movement of the wiper assembly relative to the pad assembly. 
     
     
       22. The system of  claim 18  further comprising a biasing spring coupled to the tool body for biasing the tool body toward the borehole wall. 
     
     
       23. The system of  claim 16  wherein the optical characteristic of the first MOE is at least one selected from the group consisting of: total organic content (TOC); maturation of the shale; vitrinite reflectivity; kerogen type; and amount of a particular kerogen type. 
     
     
       24. The system of  claim 16  wherein the first signal produced by the first detector is proportional to the first characteristic of the shale formation, and the second signal produced by the second detector is proportional to the second characteristic of the shale formation. 
     
     
       25. The system of  claim 16  wherein the second detector produces the second signal in real-time based on optically interacted electromagnetic radiation reflected from a corresponding portion of the shale formation exposed to the electromagnetic radiation directed from the light source onto the portion of the borehole wall. 
     
     
       26. The system of  claim 25  wherein the first and second MOEs are located within a disk assembly, a portion of the disk assembly is disposed within an optical path between the light source and the first detector, and the system further comprises:
 a motor coupled to the disk assembly for rotating the disk assembly such that first MOE and second MOE are alternately placed within the optical path. 
 
     
     
       27. The system of  claim 26  wherein:
 the disk assembly further comprises a blank location within which no multivariate optical element is located; 
 the first MOE, the second MOE, and the blank location are alternately placed within the optical path as the disk assembly is rotated by the motor; and 
 the recording system records a third signal indicative of porosity during periods of time when the blank location is placed within the optical path. 
 
     
     
       28. The system of  claim 16  further comprising a biasing spring coupled to the tool body for positioning the tool body toward the borehole wall.